Capillary isotachophoresis as rapid method for determination of orthophosphates, pyrophosphates, tripolyphosphates and nitrites in food samples

Environmentally friendly, simple and sensitive isotachophoretic method to identify and quantify orthophosphates, pyrophosphates, tripolyphosphates, nitrites and nitrates in various food products was developed. Two electrolyte systems (A) and (B) were tested and applied for determination of the above ions in meat (different canned products, smoked, cooked and long-matured pork ham, headcheese) and seafood (raw and cocktail prawns, squids and different mixes of seafood) products. For nitrogen compounds, both systems fulfilled the criteria for separation, precision and recovery. The better separation of pyrophosphates (pyroP) and tripolyphosphates (tripolyP) was obtained from system (B) with the following electrolytes: leading - 10 mM hydrochloric acid + 0.02% hydroxyethylcellulose and glycine to pH = 3.0 and terminating - 10 mM phosphoric acid. This system was characterised by linearity (R2 = 0.999 for all ions), accuracy (recoveries ranged from 97 to 98% for pyroP and 95 to 97% for tripolyP), detection: 0.64 (pyroP) and 0.27 mgP L−1 (tripolyP) and quantification: 2.12 (pyroP) and 0.91 mgP L−1 (tripolyP) limits and intra-assay of relative step height RSH (1.27-10.73%) and inter-assay of RSH (3.95-11.17%). Additionally, the obtained results of phosphate additives determination were compared at the level of added phosphorus calculating as the difference between the total phosphorus and protein bound phosphate.